Circumferential flow type liquid pump

ABSTRACT

A circumferential flow liquid pump having formed in the vicinity of an impeller  4  an inner circumferential portion of a pump flow path  7  an air vent passage  31  having an opening with a step from a bottom portion  10  of the pump flow path  7  and extending in the radially inward direction and a through hole  32  for connecting the air vent passage  31  and the exterior of the pump casing assembly  1  together, having a sufficiently large cross-sectional area as compared to the air vent passage  31  and a cross-sectional configuration of a partial annular ring shape extending along the pump flow path  7 . The through hole may be a plurality of passages  33  disposed within the region of the partial annular ring shape or al passage  34  directly connected to the pump flow path  7  without having the air vent passage  31  interposed therebetween.

TECHNICAL FIELD

This invention relates to a circumferential flow liquid pump and, moreparticularly, to a circumferential flow liquid pump for use in avehicular internal combustion engine as a fuel pump for pumping a liquidfuel such as gasoline from a fuel tank.

BACKGROUND ART

FIG. 7 is a longitudinal sectional view showing a conventionalcircumferential flow liquid pump disclosed in Japanese PatentPublication No. 7-3239, for example. FIG. 8 is an enlarged sectionalview taken along line VII—VII of FIG. 7. FIG. 9 is an enlarged sectionalview taken along line IX—IX of FIG. 8.

In the figures, 1 designates an assembly of a pump casing, the assemblybeing constituted with the pump casing main body 2 and the cover 3.Within the pump casing assembly 1, an impeller 4 having vane portion 5at its outer circumferential edge is disposed, the impeller 4 beingsupported by a central shaft 6 so that it is rotatable about its centralaxis relative to the pump casing assembly 1.

The pump casing assembly 1, as shown in FIG. 8, defines a pump flow path7 of an annular band shape extending along the outer circumferentialedge of the impeller 4 and a suction port 8 and a discharge port 9opening to the opposite end portions of the pump flow path 7, the pumpcasing assembly 1 also accommodating the vane portion 5 of the impeller4 within the pump flow path 7. Describing the further details of thepump casing assembly 1, as shown in FIG. 9, an air vent passage 11opening from the bottom portion 10 of the pump flow path 7 and extendingradially with a step therebetween is provided in the vicinity of theimpeller 4 of the inner circumferential portion of the pump flow path 7of the cover 3, and a through hole 12 having a sufficiently larger crosssectional area as compared to that of the air vent passage 11 forcommunicating the air vent passage 11 to the exterior of the pump casingassembly.

The central shaft 6 of the impeller 4 is constructed as the centralshaft of the electric motor 15 connected to the circumferential liquidpump and its opposite end portions are rotatably supported by a bearing17 and a bearing 18. 19 is an end cover provided with a check valve 22and the liquid outlet 23 and holding the bracket 24. The pump casingassembly 1 and the end cover 19 are connected together by a yoke 20 ofthe electric motor 15. The yoke 20 accommodates therein a rotor 16,defines a liquid chamber 21 between the pump casing assembly 1 and theend cover 19 for storing the liquid such as a liquid fuel dischargedfrom the discharge port 9 and has assembled to its inner circumferentialportion a permanent magnet 25 serving as a stator. The liquid chamber 21is communicated with the liquid outlet 23 having the check valve 22disposed to the end cover 19, and inserted within the bracket 24 is apower supplying brush 27 brought in a sliding contact with a commutator26 of the rotor 16.

Then, the operation of the conventional circumferential flow liquid pumpwill be described.

Also, within the pump flow path 7, gas in the form of bubbles due to theevaporation of the fuel generates at the liquid contacting surface ofthe vane portion 5 and the impeller 4 and tends to flow out into theliquid chamber 21. If these bubbles of gas flow into the liquid chamber21 and reaches the internal combustion engine, various troubles canhappen. Therefor, the arrangement is such that the gas in the form ofthe bubbles is discharged out of the pump casing assembly 1 as much aspossible by the air vent passage 11 open to the inner circumferentialportion of the pump flow path 7 and the vicinity of the impeller 4 andthe through hole 12.

This function will be described in more detail below. During theoperation of the pump, the gas in the form of the bubbles of the fuelvapor, which is generated at the contacting surface between the liquidsuch as the fuel and the vane portion 5 of the impeller 4 within thepump flow path 7, is collected at the inner circumferential portion ofthe pump flow path 7 in the vicinity of the impeller 4 due to thecentrifugal force and the difference in specific weight from the liquidfuel and flows together with the liquid through the pump flow path 7clockwise as viewed in FIG. 8 or in the same direction as the directionof rotation of the impeller 4.

When the gas bubbles reach about the air vent passage 11 which opens atthe inner circumferential portion of the pump flow path 7 in thevicinity of the impeller 4 with a step raised from the bottom portion 10of the pump flow path 7 and which extends in the direction coincidingwith the direction of whirling flow 13 generated by the impeller 4within the pump flow path 7, then the gas collected in the vicinity ofthe impeller 4 due to the static pressure within the pump flow path 7due to the pumping action and the dynamic pressure due to the whirlingflow 13 generated by the impeller 4 within the pump flow path 7 isforced to be introduced into the air vent passage 11. The introduced gasis discharged out of the pump casing assembly 1 through the through hole12 having a cross sectional area sufficiently larger than that of theair vent passage 11.

In the conventional circumferential liquid pump as above described, ifthe bubbles of the fuel vapor is generated within the pump flow path andaccumulated within the pump flow path 7, the so-called vapor lock maygenerate, impeding the flow of the liquid fuel and significantlydecreasing the pump discharge rate. In view of these problems, theconventional circumferential flow liquid pump is arranged to dischargethe bubbles out of the pump casing assembly through the air vent passage11 open to the inner circumferential portion of the pump flow path 7 andin the vicinity of the impeller 4 as well as the through hole 12.

With the above structure, the depth (H in FIG. 9) of the air ventpassage 11 must be made small, and in order not to increase the flowpath resistance against the gas flowing through the air vent passage 11,it is desirable that the length of the air vent passage 11 is as shortas possible. However, since the cross section of the through hole 12 iscircular and the cross section of the air vent passage 11 is flat, theside wall of the air vent passage 11 for communicating the pump flowpath 7 and the through hole 12 together are inevitably long. Therefore,under a bad condition in which a lot of fuel vapor is generated, the gasin the form of bubbles of the fuel vapor may not sufficiently dischargedoutside of the pump casing assembly 1, leading to a fear that thegeneration of the vapor lock cannot completely be prevented.

This invention has been made to solve the above discussed problems andhas as its object the provision of an improved circumferential flowliquid pump arranged such that the gas such as the fuel vapor bubblesgenerated within the pump flow path is ensured to be discharged from thepump flow path to the outside of the pump casing assembly and there isno fear that the vapor lock generates.

According to the present invention, the circumferential flow liquid pumpcomprises an impeller having a vane portion in an outer circumferentialportion thereof, a pump casing assembly rotatably supporting theimpeller and defining therein a pump flow path of an arcuate band-likeshape extending along an outer circumferential portion of the impellerand an suction port and a discharge port open at the opposite endportions of the pump flow path, and an air vent hole defined in the pumpcasing assembly which opens at one end thereof in an innercircumferential portion of the pump flow path in the vicinity of theimpeller and at a position radially inwardly spaced from the bottomportion of the pump flow path, opens at the other end thereof to theexterior of the pump casing assembly at a position radially inward ofthe opening at the one end and which has a cross-sectional configurationdisposed within a region of a partial annular ring shape extending alongthe pump flow path and a sufficiently large cross-sectional area.

Also, the air vent hole may comprise a radial passage extending from theone end thereof in a radially inward direction and an axial passageconnected at its one end to the other end of the radial passage and openat is the other end to the exterior of the pump casing assembly.

Also, the air vent hole may comprise a radial passage extending from theone end thereof in a radially inward direction and a plurality of axialpassages each connected at its one end to the other end of the radialpassage and open at its the other end to the exterior of the pump casingassembly and disposed within the region of a partial annular ring shape.

Further, the air vent hole m ay comprise an axial passage directlyextending from the one end and opening at its the other end to theexterior of the pump casing assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional,view of a circumferential liquid pumpof the first embodiment of the present invention;

FIG. 2 is an enlarged sectional view taken along line II—II of FIG. 1;

FIG. 3 is an enlarged sectional view taken along line III—III of FIG. 2;

FIG. 4 is a sectional view of the pump casing assembly showing thecircumferential liquid pump of the second embodiment of the presentinvention;

FIG. 5 is a sectional view of the pump casing assembly showing thecircumferential liquid pump of the third embodiment of the presentinvention;

FIG. 6 is an enlarged sectional view taken along line VI—VI of FIG. 5;

FIG. 7 is a longitudinal sectional view showing a conventionalcircumferential flow liquid pump;

FIG. 8 is an enlarged sectional view taken along line VIII—VIII of FIG.7; and

FIG. 9 is an enlarged sectional view taken along line IX—IX of FIG. 8.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a longitudinal sectional view of a circumferential liquid pumpof the first embodiment of the present invention. FIG. 2 is an enlargedsectional view taken along line II—II of FIG. 1. FIG. 3 is an enlargedsectional view taken along line III—III of FIG. 2. In the FIGS. 1-10,13, 15-27 are the components similar to those of the above-describedconventional device, so that their explanation will be omitted.

In the figures, as shown in FIG. 3, the cover 3 of the pump casingassembly 1 has formed therein an air vent passage 31 (shown in FIG. 2)which opens in the vicinity of the impeller 4 in the innercircumferential portion of the pump flow path 7 with a raised step fromthe bottom portion 10 of the pump flow path 7 (a distance from thebottom portion 10 to the position spaced apart in the circumferentiallyinward and toward the impeller 4) and which extends in the radialdirection, the cover 3 also has formed therein a through hole 32 havinga sufficiently large cross-sectional area as compared to that of the airvent passage 31 for communicating the air vent passage 31 to theexterior of the pump casing assembly 1, which through hole 32 has anelongated circular shape extending along the pump flow path 7. The airvent passage 31 and the through hole 32 together constitute an air venthole 30 which opens at one end thereof in an inner circumferentialportion of the pump flow path 7 in the vicinity of the impeller 4 and ata position radially inwardly spaced from the bottom portion 10 of thepump flow path and which opens at the other end thereof to the exteriorof the pump casing assembly 1 at a position radially inward of theopening at the one end. The cross-sectional configuration of this airvent hole 30 is within a region of a partial annular ring shapeextending along the pump flow path and a sufficiently largecross-sectional area including the opening at one end in the pump flowpath 7 as shown in FIG. 2.

The area of the cross section of the air vent passage 31 and the throughhole 32 depends upon the pump size. For a typical passenger car, the airvent passage 31 has a rectangular cross-sectional shape having a width W(shown in FIG. 2) of 4 mm, a depth H (shown in FIG. 3) of 0.2 mm, forexample, and the through hole has an elongated circular cross-sectionalshape having a larger diameter of 4 mm and a shorter diameter of 1 mm,for example.

In the circumferential flow liquid pump having the above-describedconstruction, the impeller 4 is driven by the electric motor 15 to berotated in the clockwise direction as viewed in FIG. 2, whereby theliquid such as a liquid fuel is sucked from the suction port 8 at oneend portion of the pump flow path 7. The sucked liquid flows through thepump flow path 7 in the clockwise direction as viewed in FIG. 2 andflows into the liquid chamber 21 from the discharge port 9 at its theother end.

During the operation of the pump, the gas in the form of the bubbles ofthe fuel vapor, which is generated at the contacting surface between theliquid such as the fuel and the vane portion 5 of the impeller 4 withinthe pump flow path 7, is collected at the inner circumferential portionof the pump flow path 7 in the vicinity of the impeller 4 due to thecentrifugal force and the difference in specific weight from the liquidfuel and flows together with the liquid through the pump flow path 7clockwise as viewed in FIG. 2 or in the same direction as the directionof rotation of the impeller 4.

When the gas bubbles reach about the air vent passage 31 which opens atthe inner circumferential portion of the pump flow path 7 in thevicinity of the impeller 4 with a step raised from the bottom portion 10of the pump flow path 7 and which extends in the direction coincidingwith the direction of whirling flow 13 generated by the impeller 4within the pump flow path 7, then the gas collected in the vicinity ofthe impeller 4 due to the static pressure within the pump flow path 7due to the pumping action and the dynamic pressure due to the whirlingflow 13 generated by the impeller 4 within the pump flow path 7 isforced to be introduced into the air vent passage 31.

The introduced gas is discharged out of the pump casing assembly 1through the through hole 32 communicated with the air vent passage 31and having a cross sectional area sufficiently larger than that of theair vent passage 31. It is to be noted that since the through hole 32 isarranged to be in an elongated circular configuration extending alongthe aforementioned pump flow path 7, the through hole 32 can bepositioned close to the pump flow path 7 which makes the air ventpassage 31 short, whereby the flow path resistance against the gas uponits passage through the air vent passage can be significantly decreased.

FIG. 4 is a sectional view of the pump casing assembly showing thecircumferential liquid pump of the second embodiment of the presentinvention. In the figures, 2, 4-9 are the components similar to those ofthe above-described conventional device, so that their explanation willbe omitted.

While the through hole 32 in the above first embodiment is arranged tobe in an elongated circular configuration extending circumferentiallyalong the afore-mentioned pump flow path 7, in the second embodiment, aplurality of through holes 33 are arranged within a partial annular ringshape extending circumferentially along the pump flow path 7. With suchconstruction, a similar function to that of the first embodiment can beachieved.

FIG. 5 is a sectional view of the pump casing assembly showing thecircumferential liquid pump of the third embodiment of the presentinvention. FIG. 6 is an enlarged sectional view taken along line VI—VIof FIG. 5. In the FIGS. 1—10, 13, 20 are the components similar to thoseof the above-described conventional device, so that their explanationwill be omitted.

The air vent hole in this embodiment is a through hole 34, which, asshown in FIG. 6, opens in the vicinity of the impeller 4 in the innercircumferential portion of the pump flow path 7 of the cover 3 with araised step from the bottom portion 10 of the pump flow path 7 andextends directly therefrom in the axial direction to communicate thepump flow path 7 and the exterior of the pump casing assembly 1. Also,the cross-sectional configuration of the through hole 34 is as shown inFIG. 5. is a partial annular ring shape or an elongated circular shapeextending along the pump flow path 7 and has a sufficiently largecross-sectional area.

Also in this embodiment, the cross-sectional area of the through hole 34depends upon the size of the pump. For a typical passenger car, thethrough hole 34 has an elongated circular cross-sectional shape having alarger diameter of 4 mm and a smaller diameter of 1 mm, for example.

Also with such the arrangement, a similar function to that of the firstembodiment can be achieved.

APPLICABILITY IN INDUSTRY

The circumferential flow liquid pump of the present invention has thestructure as above described, so that the gas generated within the pumpflow path is discharged to the exterior of the pump casing assemblywithout being affected by the flow path resistance. Therefore, thedischarge of gas generated within the pump flow path to the exterior ofthe pump casing assembly can be achieved at a high efficiency andreliability, whereby the building up of the gas in the pump flow pathand the generation of the vapor lock can be suppressed and the decreaseof the pump discharge rate can be minimized.

What is claimed is:
 1. A circumferential flow liquid pump comprising: animpeller having an outer circumferential portion in which a vane portionis provided; a pump casing assembly rotatably supporting said impeller,said pump casing defining (1) a pump flow path having an arcuateband-like shape extending along said outer circumferential portion ofsaid impeller and (2) a suction port and a discharge port thatrespectively open at opposite end portions of said pump flow path; andan air vent hole defined in said pump casing assembly, said air venthole having (1) a first end that opens to an inner circumferentialportion of said pump flow path at a position radially inwardly spacedfrom a bottom portion of said pump flow path, and (2) a second end thatopens to the exterior of said pump casing assembly at a positionradially inward of said first end; wherein said air vent hole has across-sectional configuration that (1) extends along said pump flowpath, (2) defines a longitudinal axis that is parallel to a longitudinalaxis of said pump flow path along an entire length of saidcross-sectional configuration, and (3) is spaced apart from said suctionport and said discharge port.
 2. A circumferential flow liquid pump asclaimed in claim 1, wherein said air vent hole comprises (1) a radialpassage extending from said first end in a radially inward direction and(2) an axial passage extending from said radial passage to said secondend.
 3. A circumferential flow liquid pump as claimed in claim 1,wherein said air vent hole comprises (1) a radial passage extending fromsaid first end in a radially inward direction and (2) a plurality ofaxial passages extending from said radial passage to said second end. 4.A circumferential flow liquid pump as claimed in claim 1, wherein saidair vent hole comprises an axial passage extending along only an axialdirection from said first end to said second end.
 5. A circumferentialflow liquid pump comprising: an impeller; and a pump casing rotatablysupporting said impeller, said pump casing defining (1) a pump flow pathextending along an outer circumference of said impeller, (2) a suctionport and a discharge port that open into said pump flow path, and (3) avent hole having a first end that opens into said pump flow path, and asecond end that opens to the exterior of said pump casing; wherein saidvent hole has a cross-sectional configuration that (1) extends alongsaid pump flow path, (2) defines a longitudinal axis that is parallel toa longitudinal axis of said pump flow path along an entire length ofsaid cross-sectional configuration, and (3) is spaced apart from saidsuction port and said discharge port.
 6. A circumferential flow liquidpump as claimed in claim 5, wherein said vent hole comprises (1) aradial passage extending from said first end in a radially inwarddirection and (2) an axial passage extending from said radial passage tosaid second end.
 7. A circumferential flow liquid pump as claimed inclaim 5, wherein said vent hole comprises (1) a radial passage extendingfrom said first end in a radially inward direction and (2) a pluralityof axial passages extending from said radial passage to said second end.8. A circumferential flow liquid pump as claimed in claim 5, whereinsaid vent hole comprises an axial passage extending along only an axialdirection from said first end to said second end.